Patient immobilization is essential for the safety and efficacy of radiation therapy (RT). In particular, patients undergoing RT typically are disposed on a treatment table or couch associated with a LINAC or other the radiation therapy apparatus. Various couch-tops and overlays are commercially available for disposition on the treatment table, with the patient being disposed on the couchtop/overlay. Such couchtops and overlays commonly include indexing features. Fixation or immobilization devices are available for use with the couchtops/overlays to position the patient in the same anatomic position and location on the treatment table as on the planning table (i.e., the table upon which the radiation treatment plan was established). Examples of such patient positioning/fixation devices are head and neck positioning/fixation devices (e.g., thermoplastic masks), breast and thorax positioning/fixation devices, and hip and pelvic region positioning/fixation devices. Many of such devices, as well as other miscellaneous positioning aids, e.g., cushions, wedges, etc., for use on the treatment couchtop/overlay are available from the assignee of this invention, Civco Medical Solutions (hereinafter “CIVCO”), and are shown in its “Radiation Oncology Sourcebook” ©2007. The treatment planning table has matching indexing features to the RT treatment table, and the RT treatment table is registered to the RT treatment beam. This combination enables accurate planning and delivery of radiation therapy.
Other manufacturers also provide couchtops/overlays with various types of indexing systems and positioning/fixation devices to be used with such indexing systems since patient immobilization is essential for the safety and efficacy of radiation therapy.
Some table overlays are commonly employed for extending the head and neck region off the end of a standard built in RT treatment table. Such table overlays are typically of lower density than the treatment table and as uniform in density as possible. Immobilization or fixation devices are secured to these overlays via attachment hardware to hold the particular portion of the patient's anatomy in the desired position for the radiation therapy. The attachment hardware must be employed because the fixation devices must be removable for patient safely and so that the patient may be exactly repositioned at different times for planning and the radiation treatment which may involve multiple sessions.
One type of immobilizing and positioning device used for treating the head and neck region is the thermoplastic mask. This device is a perforated mask that is heated and may then be stretched over the upper torso, head and neck areas and be closely molded to individual anatomy to provide a very secure fit. Typically, the thermoplastic material must be attached to a bracket of some sort to enable handling, fitting of the mask and fixation of the mask to the treatment table. Presently available attachment hardware for the patient positioning and fixation devices that must be used involve brackets and locking features that create focal areas of irregularly shaped (typically plastic) mass that are problematic for both treatment planning and radiation delivery. In particular, the bracket and attachment mechanisms are often in line with the treatment beam and cause attenuation and distortions of the therapeutic beam of energy being delivered that are not easily managed therapeutically. This is a problem for all currently available mask immobilization devices and other related devices that may end up in the treatment path.
Thus, a need presently exists for the solution to the problem of having to image, simulate/plan and treat tumors with RT and having the treatment path obstructed by irregularly shaped and variable density components that are currently used for attaching patient fixation hardware, since such attachment components both attenuate and distort the treatment beam in and undesirable manner that reduces the accuracy of both targeting and dose delivery to the target area within a patient.
The subject invention addresses that need by providing a system including an overlay that eliminates the irregular extra mass of the attachment hardware essentially by attaching the fixation Material or devices directly to the overlay itself. By eliminating these irregular devices of varying thickness and shape and mass (varying density of material in some cases), the imaging is improved, planning becomes simpler because of the reduced calculations required with the cleaner interference platform, and the safety and accuracy of the RT treatment is improved with reduced interference of the treatment beam.
All references cited and/or identified herein are specifically incorporated by reference herein.